| 摘要 |
PURPOSE:To use a semiconductor integrated circuit in a PLL circuit to cope with an external device of the new system while keeping the compatibility with an external device of the old system by selecting a first enable signal or a second enable signal by a switching signal. CONSTITUTION:A first enable signal S2' obtained from a shift register 3', a second enable signal S2 obtained from an enable terminal P2, and a switching signal S7 obtained from a switching input terminal P7 are taken in by a switching circuit 5. One of first and second enable signals S2 and S2' is outputted in accordance with the switching signal S7. Consequently, the first enable signal S2' or the second enable signal S2 is selected on demand. Thus, this circuit can cope with the external device of the new system while keeping the compatibility with the external device of the old system. |
